As is well known, sanitary articles, in particular baby diapers, sanitary napkins or incontinence products for adults comprise a layer of absorbent padding enclosed in a layer of non-woven fabric and a waterproof layer, for example polyethylene. These components are the basic elements of an absorbent article. In addition to these basic components mentioned above, the absorbent articles comprise further additional components (such as elastic bands, fecal barriers and side wings) which make the structure, as well as the realization, complex.
A known type of packaging machine for making sanitary absorbent articles comprises an advancing line of a continuous strip of impermeable material along which a plurality of operating units are disposed which feed the continuous web both of the basic components and of the additional components intended to complete the absorbent article.
Each operating unit comprises a processing apparatus that receives a component and processes the same component (for example by cutting the component into discrete lengths if the component is fed as a continuous strip to the processing apparatus) and a transferring and rotating apparatus that receives the component from the processing apparatus, when the processing has ended, and applies the component to the strip of impermeable material, picking up the component in a first orientation and releasing it in a second orientation, rotated with respect to the first orientation.
Generally, the transferring and rotating apparatus comprises a central drum which rotates around a central axis of rotation and supports, by means of a plurality of radially extending arms, respective suction retaining heads to hold the component during the transfer. Each suction retaining head can rotate further relative to the central drum itself to change the orientation of the component between a pickup station, in which the basic component is received by the transfer element, and a release station, in which the base component is released to a subsequent apparatus.
During the rotation of the central drum, the position of the suction retaining head with respect to a rotation axis of the drum itself is modified radially between a first radius, at the pickup station, and a second radius, at the release station, for varying the linear speed of the retaining head itself, and then accelerate or decelerate the components during the transfer from the pickup station to the release station.
In this way it is possible to pick up a succession of basic components from the pickup station spaced at a certain interval, commonly also called step or “pitch”, and deliver the same components in the release station spaced by a different interval.
The rotation of the radial arms with respect to the central drum, the rotation of the retaining heads with respect to the radial arms and the variation of the radial position of each retaining head are mechanically controlled by means of respective driving cams.
The variation of the radial position of each retaining head can cause excessive stresses in the retaining head, and then excessive wear of the same retaining head that may be subject to breakage or undesired malfunctions.
Furthermore, during a format change operation, i.e. during an operation that changes the packaging machine to vary the type of sanitary absorbent articles which are to be packaged, it is often necessary to modify the law of motion of the suction retaining heads to adapt this law of motion to a different size and/or location of the components that are treated.
Modification of the law of motion of the retaining heads requires the replacement of some mechanical components, typically at least the corresponding cams, and such replacement is particularly long and complex due to the positioning of the cams themselves towards the base of the transferring and rotating apparatus, which requires disassembly and subsequent assembly of numerous additional mechanical components and a step of configuration that is rather lengthy and requires the intervention of a skilled technician.
EP 2659869 A1 discloses an apparatus for transferring and rotating an object.